<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<script>
var arr = ["a", 20, true, 2000];
var str = arr.toString();  // 用逗号连接每个元素的字符串
console.log(str);
var s1 = arr.join("abc");    // 返回的也是字符串, 用 参数连起来
console.log(s1);
</script>
</body>
</html>